JP2004253929A - Cathode ray tube assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode-ray tube assembly which reduces the power consumption due to the brightness correction. <P>SOLUTION: The cathode-ray tube assembly adds a correction voltage to a video signal to correct the brightness reduction at the screen peripheral area. It comprises a correction voltage output unit 40 for outputting the correction voltage synchronously with the scan position and a brightness correction controller 50 for controlling the execution of the brightness correction. The controller 50 detects a mean screen brightness for a specified time using a brightness detector circuit 51, executes the brightness correction as usual when the mean screen brightness is not less than a reference value, or controls to set off the output of the correction voltage output unit 40, if the mean screen brightness is less than the reference value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cathode ray tube device, and more particularly to a cathode ray tube device that corrects a decrease in luminance at a peripheral portion of a screen by adding a correction voltage to a video signal.
[0002]
[Prior art]
2. Description of the Related Art In a cathode ray tube (hereinafter, referred to as "CRT") device, it is known that when an image is displayed on a screen, the brightness is reduced at a peripheral portion of the screen. This is said to be caused by the fact that the electron beam trajectory is elongated in an elliptical shape due to the increase in the electron beam trajectory as the deflection angle increases, and the electron beam density becomes low. Further, since the panel portion has a thicker structure as it approaches the screen peripheral portion, the transmittance of the light emitted from the electron beam decreases as it approaches the screen peripheral portion, and the brightness decreases at the screen peripheral portion. It has contributed. Therefore, by adding the parabolic correction voltage synchronized with the horizontal scanning to the contrast control voltage and increasing the amount of the emitted electron beam at the time of scanning the peripheral portion of the screen, the luminance reduction at the peripheral portion of the screen is corrected. (For example, Patent Document 1).
[0003]
[Patent Document 1]
JP-A-5-292426
[0004]
[Problems to be solved by the invention]
As described above, in the conventional CRT device, although it is a highly evaluated technique for correcting a decrease in luminance at the peripheral portion of the screen, the luminance is constantly corrected during scanning. However, when a low-brightness image is displayed in which the entire screen is dark and the luminance drop at the periphery of the screen is not so noticeable, a disadvantage that power is wasted is rather generated.
[0005]
The present invention has been made in view of the above-described problems, and provides a CRT device that can effectively reduce power consumption due to luminance correction while performing luminance correction around a screen. The purpose is.
[0006]
[Means for Solving the Problems]
On a screen composed entirely of bright colors, the brightness of the entire screen is high, and if brightness correction is not performed, the brightness at the periphery of the screen will decrease significantly. Is low in the center of the screen, and the brightness decrease in the periphery of the screen is not so noticeable. Therefore, it is considered that the necessity of executing the brightness correction is low. Also, on a screen where light-colored characters are displayed on a dark background, even if light-colored characters are displayed at the periphery of the screen, the background color is dark, and the contrast between light and dark colors is strong. Since it is hardly possible to recognize bright-colored characters due to a decrease in luminance, it is considered that the need for luminance correction is low.
[0007]
Therefore, a cathode ray tube device according to the present invention includes a correction voltage output unit that outputs a correction voltage in synchronization with scanning, and a luminance correction control unit that controls execution of luminance correction. In addition to detecting the average screen luminance over time, when the average screen luminance is less than the reference value, control is performed to turn off the output of the correction voltage output means.
[0008]
In the above configuration, a brightness correction control unit that controls execution of brightness correction is provided, and when the average screen brightness for a predetermined time becomes less than the reference value, the output of the correction voltage output unit is turned off, and control for not performing brightness correction is performed. do. Therefore, for example, when the necessity of performing the luminance correction is low, such as a screen in which the entire screen is dark and the luminance decrease in the peripheral part of the screen is not so conspicuous, the control that does not perform the luminance correction is performed. Can be reduced.
[0009]
Here, it is preferable that the brightness correction control means includes a circuit for integrating the anode current, and detects the average screen brightness based on the integrated value of the anode current for a predetermined time. Since the average screen luminance can be easily detected by integrating the anode current correlated with the luminance, such a configuration can facilitate the circuit configuration for detecting the average screen luminance.
[0010]
Specifically, the brightness correction control means includes an automatic brightness limiting circuit for preventing the high voltage circuit from being overloaded by reducing the amount of electron beam emission based on the integrated value of the anode current and limiting the brightness. Preferably, the average screen luminance is detected based on the integrated value of the anode current detected by the automatic luminance limiting circuit. The automatic brightness limiting circuit is usually provided in the cathode ray tube device and has a function of integrating the anode current. Therefore, the automatic brightness limiting circuit should be configured to detect the average screen brightness based on the integrated value. Thereby, the manufacturing cost of the cathode ray tube device can be suppressed.
[0011]
Further, the correction voltage output means has a dynamic focus circuit that generates a focus voltage that gradually increases as the deflection angle of the electron beam increases, and outputs the dynamic focus voltage generated by the dynamic focus circuit as a correction voltage. preferable. In such a configuration, the voltage generated by the dynamic focus circuit is used as a correction voltage for luminance correction, and there is no need to separately form a circuit for generating a parabolic correction voltage unlike a conventional cathode ray tube device. The manufacturing cost of the pipe device can be reduced.
[0012]
Alternatively, it is preferable that the correction voltage output means outputs a voltage applied to both ends of an S-shaped correction capacitor attached to an S-shaped correction circuit for correcting distortion of the deflection amount of the electron beam as a correction voltage. In such a configuration, a voltage applied to both ends of the S-shaped correction capacitor is used as a correction voltage for luminance correction, and it is not necessary to separately form a circuit for generating a parabolic correction voltage unlike a conventional cathode ray tube device. Therefore, the manufacturing cost of the cathode ray tube device can be reduced.
[0013]
Another cathode ray tube device according to the present invention is characterized in that a dynamic focus voltage generated by a dynamic focus circuit is used as a correction voltage. In such a configuration, the voltage generated by the dynamic focus circuit is used as a correction voltage for luminance correction, and there is no need to separately form a circuit for generating a parabolic correction voltage unlike a conventional cathode ray tube device. The manufacturing cost of the pipe device can be reduced.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a CRT device according to the present invention will be described with reference to the drawings.
(Embodiment 1)
First, the configuration of the CRT device will be described with reference to FIG. FIG. 1 is a diagram illustrating a circuit configuration of the CRT device 10. The CRT device 10 includes a CRT 20, an RGB processor 30 that performs video signal processing, a correction voltage output unit 40 that outputs a correction voltage, a luminance correction control unit 50 that controls the output of the correction voltage output unit 40, and a contrast adjustment unit. And a bias resistor 60 that operates.
[0015]
The luminance correction control unit 50 includes a luminance detection circuit 51 that detects an average screen luminance for a predetermined time, a comparator 52 that compares the average screen luminance with a reference value, and a correction voltage output based on a comparison result by the comparator 52. And an open collector type inverter (hereinafter, referred to as “OC”) 53 for turning on / off the output of the unit 40.
The output terminal of the luminance detection circuit 51 is connected to the negative input terminal of the comparator 52, and the reference voltage Vc is applied to the positive input terminal. The output terminal of the comparator 52 is connected to the OC 53 at a contact a via a resistor 54, and the contact a is grounded via a resistor 55. Note that the output terminal of the OC 53 is the output terminal of the luminance correction control unit 50.
[0016]
The correction voltage output unit 40 includes a correction voltage generation circuit 41 that generates a panoramic correction voltage in synchronization with horizontal scanning, a transistor 42 that amplifies the output of the correction voltage generation circuit 41, a driving power supply Vt for the transistor 42, And a capacitor 43 for cutting the DC component of the output waveform. The output of the correction voltage generation circuit 41 is connected to the base of the transistor 42, the emitter is grounded via the resistor 44, and the collector is connected to the output terminal of the luminance correction control unit 50 at the contact b. The collector of the transistor 42 is connected to the drive power supply Vt via the resistor 45 and to one end of the capacitor 43. The other end of the capacitor 43 is connected to the bias resistor 60, and the correction voltage output from the correction voltage output unit 40 is added to the contrast control voltage and input to the RGB processor 30.
[0017]
Hereinafter, the operation of the CRT device 10 will be described with reference to FIG. The CRT 20 is vertically scanned from the upper end to the lower end of the screen while being repeatedly horizontally scanned from the left end to the right end of the screen by a horizontal synchronization circuit and a vertical synchronization circuit (not shown). In synchronization with this scanning, the video signal is separated into each color of RGB by the RGB processor 30 and applied to the cathodes of three electron guns arranged in line. As a result, the video signal is displayed on the screen of the CRT 20 as a video.
At the time of this display operation, the output created by the correction voltage output unit 40 is applied to the RGB processor 30 and added to each of the RGB video signals.
[0018]
Here, assuming that the luminance correction control unit 50 is not operating, the correction voltage generated by the correction voltage generation circuit 41 is a panorama synchronized with horizontal scanning, so that the scanning position is from the left end or right end of the screen. In some cases, the voltage generated by the correction voltage generation circuit 41 is high, and decreases as the scanning position approaches the center of the screen, and is amplified by the transistor 42. The DC component is cut off from this voltage through the capacitor 43, and the AC component is superimposed on the contrast control voltage obtained from the bias resistor 60 and applied to the RGB processor 30. Therefore, the video voltage to which the correction voltage has been added is subjected to modulation such that the luminance is high around the screen, and becomes lower toward the center.
[0019]
This modulation is always performed when the brightness correction control unit 50 does not operate. Therefore, as described in the related art section, when the entire screen is dark and the brightness decrease is not so conspicuous, power is wasted. However, in this embodiment, the brightness correction control unit 50 operates as follows to eliminate waste of power. That is, the luminance correction control unit 50 detects the average screen luminance during a predetermined time, and when the average screen luminance is higher than the reference value, causes the correction voltage output unit 40 to output the correction voltage and executes the luminance correction as described above. However, when the average screen luminance is lower than the reference value, the control of turning off the output of the correction voltage output unit 40 and not executing the luminance correction is performed.
[0020]
The brightness detection circuit 51 has a brightness capacitor that integrates the anode current flowing for a predetermined time, and the capacity of the brightness capacitor is sufficiently large with respect to the amount of inflow of the anode current. The voltage between both ends of the luminance capacitor changes in balance with the discharging action of discharging electric charges. Here, at the time of scanning, the anode current changes according to the amount of the electron beam applied to each point of the screen, that is, the luminance, and the voltage across the luminance capacitor is the amount of the anode current flowing through the circuit in a predetermined time. Since it is substantially proportional to the integrated value, the voltage between both ends of the luminance capacitor indicates the average screen luminance in a predetermined time.
[0021]
When a high-luminance video signal is input to the RGB processor 30, a large amount of electron beams are emitted from the electron gun of the CRT 20, and a high-luminance screen is displayed on the screen. At this time, since a large anode current flows, in the luminance capacitor of the luminance detecting circuit 51, the charging operation is larger than the discharging operation, and the voltage across the luminance capacitor indicating the average screen luminance increases. When the voltage across the luminance capacitor is higher than the reference voltage Vc, the comparator 52 outputs a Low signal to the OC 53. The output of the OC 53 that has received the Low signal is in an open state. As a result, the drive voltage Vt is applied to the contact b via the resistor 45, so that the transistor 42 is operated. The output of the correction voltage generation circuit 41 is amplified by the transistor 42, and the DC voltage is amplified by the coupling capacitor 43. Is cut off, the AC component is superimposed on the contrast control voltage as a correction voltage, thereby performing luminance correction.
[0022]
Here, when a video signal whose entire screen is dark is input to the RGB processor 30, the amount of the electron beam emitted from the electron gun of the CRT 20 decreases, and the anode current also decreases. Then, in the luminance capacitor of the luminance detection circuit 51, the discharging action becomes stronger than the charging action, so that the voltage across the luminance capacitor indicating the average screen luminance decreases. When the voltage between both ends falls below the reference voltage Vc, a High signal is transmitted from the comparator 52 to the OC 53. Then, the output of the OC 53 is grounded and the potential of the contact b becomes 0 V, so that the transistor 42 does not operate and the correction voltage generation circuit 41 does not output the correction voltage. As a result, only the contrast control voltage is input to the RGB processor 30, and the image is displayed by scanning the electron beam without adding the correction voltage. At this time, no correction has been made to reduce the decrease in luminance at the periphery of the screen, but the displayed image is dark in the entire screen and the luminance at the center of the screen is low. Hardly noticeable, no problem.
[0023]
As described above, the CRT device 10 according to the present embodiment performs the brightness correction on the screen having the high average screen brightness, but performs the brightness correction on the screen having the relatively low average screen brightness and the low necessity of the brightness correction. Since the control that does not output the correction voltage and does not execute the luminance correction is performed, the power consumption can be reduced as compared with the conventional CRT device that uniformly executes the luminance correction.
[0024]
Here, an ABL circuit is given as an example of the luminance detection circuit 51 that detects the average screen luminance during a predetermined time. The ABL circuit is usually provided in a CRT device in order to prevent a large anode current from flowing into the picture tube when the luminance becomes abnormally high, thereby overloading the high voltage circuit and damaging the horizontal output transistor and the like. . The ABL circuit usually has a capacitor for integrating the anode current, detects an average screen luminance for a predetermined time, and when this exceeds a predetermined value, modulates the cathode voltage to reduce the emission amount of the electron beam. To prevent the above adverse effects. Therefore, by using the function of detecting the average screen luminance based on the anode current by the ABL circuit in combination with the luminance detection circuit 51, the manufacturing cost of the CRT device 10 can be reduced.
[0025]
The magnitude of the reference voltage Vc can be set arbitrarily. When the reference voltage Vc is set to a large value, the number of cases in which the correction voltage is not output increases, which is beneficial from the viewpoint of power consumption.
On the other hand, if the reference value is set to a small value, it is possible to reduce the number of screens in which luminance is noticeably reduced at the periphery of the screen. However, since the correction voltage is output and the luminance is corrected even for a relatively dark screen, power consumption is reduced. Is disadvantageous for Therefore, the reference voltage Vc is set to the best value based on the balance between the power consumption and the allowable range of the luminance reduction.
[0026]
As described above, the CRT device 10 according to the present embodiment detects the average screen luminance during a predetermined time and performs control not to execute the luminance correction when the entire screen is dark and the necessity of the luminance correction is low. Consumption can be reduced.
[0027]
(Embodiment 2)
Next, a CRT device according to a second embodiment of the present invention will be described. The CRT device according to the second embodiment has the same basic configuration as that of the CRT device according to the first embodiment, except that a dynamic focus circuit (hereinafter, “DAF circuit”) is used as the correction voltage generation circuit 41. ").) The DAF circuit is originally provided in a CRT device for focusing an electron beam on a single point on a phosphor screen in response to a change in the deflection angle. A high voltage is generated at the left end or the right end, and a lower voltage is generated as the scanning position approaches the center of the screen. Therefore, when a voltage generated by the DAF circuit is used as a correction voltage for luminance correction, it is possible to improve luminance reduction in a peripheral portion of a screen.
[0028]
Further, by using a DAF circuit that generates a high voltage when the scanning position is at the upper or lower end of the screen in synchronization with the vertical scanning and generates a lower voltage as the scanning position approaches the center of the screen, the DAF circuit synchronizes with the vertical scanning. Therefore, since such a voltage is superimposed, a reduction in luminance occurring at the upper and lower ends of the screen is also improved. In this case, in a CRT in which the thickness of the screen panel in the vertical direction is thin at the center of the screen and thick at the periphery of the screen, it is possible to effectively correct the decrease in light transmittance due to the thickness of the screen panel at the periphery of the screen. It will be effective.
[0029]
As described above, when the voltage generated by the DAF circuit is added to the video signal, the decrease in luminance at the peripheral portion of the screen is improved. In addition, since the DAF circuit is normally provided in a CRT device, By also using the correction voltage generation circuit 41, the manufacturing cost of the CRT device 10 can be reduced.
[0030]
Further, as shown in FIG. 2, by forming a smoothing circuit including a zener diode 46, a resistor 47 and a resistor 48 between the DAF circuit 41 and the transistor 42, the output waveform of the DAF circuit 41 is The shape can be smoothed.
As a result, the shape of the correction voltage corresponds to the thickness of the screen panel in the case of a CRT having a flat screen panel in which the thickness is uniform near the center of the screen and the thickness at the periphery of the screen is greatly increased. Because of this, it is possible to improve a decrease in luminance at the periphery of the screen, which is caused by a decrease in light transmittance due to an increase in the thickness of the screen panel.
[0031]
(Embodiment 3)
Next, a CRT device according to a third embodiment of the present invention will be described. The CRT device according to the third embodiment has the same basic configuration as that of the CRT device according to the first embodiment, but the correction voltage generation circuit 41 corrects the amount of deflection of the electron beam by S-shape. A voltage applied to both ends of the S-shaped correction capacitor in the circuit to be output is output as a correction voltage. Since the waveform of the voltage across the S-shaped correction capacitor is parabolic and synchronized with horizontal scanning, it can be used as a correction voltage for luminance correction. This eliminates the need to separately create a circuit for generating a parabolic waveform, thereby reducing the manufacturing cost of the CRT device. Further, by attaching a smoothing circuit for smoothing the waveform of the voltage between both ends of the S-shaped correction capacitor, it is possible to perform correction corresponding to a flat screen as in the CRT device according to the second embodiment. it can.
[0032]
(Embodiment 4)
2. Description of the Related Art Conventionally, in order to improve a decrease in luminance at a peripheral portion of a screen, a large number of CRT devices that perform luminance correction by adding a parabolic correction voltage to a video signal have been developed. However, since a circuit for generating a parabolic correction voltage is separately formed, there is a problem that the manufacturing cost is increased. Therefore, an object of the present embodiment is to provide a CRT device that can reduce the manufacturing cost.
[0033]
The configuration of the CRT device according to the present embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating a circuit configuration of the CRT device 11. The CRT device 11 includes a CRT 20, an RGB processor 30 that performs video signal processing, a correction voltage output unit 40 that outputs a correction voltage, and a bias resistor 60 that adjusts contrast.
The correction voltage output unit 40 includes a dynamic focus circuit (hereinafter, referred to as a “DAF circuit”) 41, a transistor 42 that amplifies the output of the DAF circuit 41, a driving power supply Vt of the transistor 42, and a DC component of the output waveform. And a capacitor 43 that cuts The output of the DAF circuit 41 is connected to the base of the transistor 42, the emitter is grounded via the resistor 44, and the collector is connected to the output terminal of the luminance correction control unit 50 at the contact b. The collector of the transistor 42 is connected to the drive power supply Vt via the resistor 45 and to one end of the capacitor 43. The other end of the capacitor 43 is connected to the bias resistor 60, and the correction voltage output from the correction voltage output unit 40 is added to the contrast control voltage and input to the RGB processor 30.
[0034]
Next, the operation of the CRT device 11 will be described. The DAF circuit 41 is provided in a CRT device to focus the electron beam on a single point on the phosphor screen in response to the change in the deflection angle, and the scanning position is synchronized with the horizontal scanning. When the screen is at the left end or the right end, a high voltage is generated, and a lower voltage is generated as the scanning position approaches the center of the screen. Therefore, the voltage generated by the DAF circuit 41 is amplified by the transistor 42, the DC component is cut off by the capacitor 43, is superimposed on the contrast control voltage, and is input to the RGB processor 30. Then, the video signal is modulated so that the luminance becomes higher at the periphery of the screen, and the decrease in luminance at the periphery of the screen is corrected.
[0035]
FIG. 4 shows a luminance correction result of the CRT device according to the present embodiment.
FIGS. 4A and 4B show the relative luminance at each position on the screen when the luminance at the center of the screen is set to 100. FIG. Note that the luminance distribution is obtained by measuring the luminance at each position on the screen when an all-white video signal is input by directly applying the sensor of the luminance meter to the screen after 15 minutes or more from the start of screen display. I asked.
At this time, the measurement was performed in a state where the external light was blocked so as not to be affected by the external light. FIG. 4A shows the luminance when the luminance correction is not performed, and FIG. 4B shows the luminance when the luminance correction is performed. As shown in FIG. 4A, the relative luminance average of the peripheral portion of the screen when luminance correction is not performed is 58.8, whereas the DAF circuit is generated as shown in FIG. 4B. The average relative luminance at the periphery of the screen when the luminance is corrected using the voltage is improved to 88.1. Therefore, it was confirmed that the luminance reduction in the peripheral portion of the screen can be corrected by using the voltage generated by the DAF circuit as the correction voltage.
[0036]
As described above, the CRT device 11 according to the present embodiment uses the voltage generated by the DAF circuit as a correction voltage for luminance correction, and separates a circuit for generating a parabolic correction voltage like a conventional CRT device. Since there is no need to form them, the manufacturing cost of the CRT device can be reduced.
In addition, by using the voltage applied to both ends of the S-shaped correction capacitor attached to the S-shaped correction circuit for correcting the distortion of the deflection amount of the electron beam as the correction voltage, the brightness reduction in the peripheral portion of the screen can be performed in the same manner as described above. Can be corrected. Since the waveform of the voltage at both ends of the S-shaped correction capacitor is parabolic and synchronized with horizontal scanning, it can be used as a correction voltage for luminance correction in the same manner as the voltage generated by the DAF circuit. This eliminates the need to separately create a circuit for generating a parabolic waveform, thereby reducing the manufacturing cost of the CRT device.
[0037]
<Modification>
As described above, the present invention has been described based on various embodiments. However, it is needless to say that the contents of the present invention are not limited to the specific examples shown in the above-described embodiments. An example can be considered.
[0038]
(1) For example, in an interlace type CRT, a screen for which luminance correction is performed or a screen which is not required to be performed by refreshing the luminance capacitor of the luminance detection circuit 51 every 1/60 second. Can be accurately determined. In the CRT 20, 30 screens are displayed per second, but in the interlaced system, field scanning is performed every 1/60 second to prevent flickering of the screen. It is formed by one field scan. Here, the brightness capacitor of the brightness detection circuit 51 is refreshed every 1/60 second in synchronization with the vertical synchronizing signal, and the integration time of the anode current is set to 1/60 second. When the average screen luminance is smaller than the reference value, the control that does not execute the luminance correction can be performed without outputting the correction voltage at the time of the second field scan. Since the first and second field scans have a correlation in luminance, it is not possible to determine whether to perform the luminance correction at the time of the second field scan based on the average screen luminance of the first field scan. It is reasonable. In this case, the anode current flowing at the time of the second field scan is integrated, and based on the result, it is determined whether or not to add the correction voltage at the time of the first field scan of the next screen. Become. Therefore, when the screen is switched from the low-luminance screen to the high-luminance screen, the luminance in the second field scanning of the low-luminance screen is low. Is not added, and the luminance at the peripheral portion of the screen is reduced. However, when the first field scan of the high luminance screen is performed, the anode current increases and the voltage across the luminance capacitor becomes higher than the reference voltage Vc. Therefore, the correction voltage is added during the second field scan of the high luminance screen. As a result, the decrease in the luminance at the peripheral portion of the screen is corrected. As described above, in the case of the high-luminance screen, during the first field scan when the screen is switched from the low-luminance screen to the high-luminance screen, the decrease in the luminance may not be corrected. In addition, since the decrease in luminance is corrected at the time of the next field scan, human eyes cannot recognize the decrease in luminance, so this is not a major problem. Accordingly, in the interlaced CRT, execution and non-execution of the brightness correction can be rationally controlled by refreshing the brightness capacitor of the brightness detection circuit 51 every 1/60 second. Accordingly, power consumption can be effectively reduced.
[0039]
(2) In the above embodiment, the brightness correction control is performed by focusing on the anode current. However, the brightness correction control may be performed by focusing on the drive voltage that is correlated with the electron beam emission amount. The drive voltage is represented by the amount of displacement of the cathode voltage, that is, the amplitude of the cathode voltage in a cathode ray tube type CRT, and the magnitude of the drive voltage is proportional to the emission amount of the electron beam. Therefore, by integrating the drive voltage for a predetermined time, it is possible to detect the average screen luminance in the predetermined time. When a high-luminance video signal is input to the RGB processor 30 and the drive voltage rises and the average screen luminance becomes equal to or higher than the reference value, the luminance correction is performed to improve the luminance decrease at the peripheral portion of the screen, and the average screen luminance is increased. Is smaller than the reference value, the brightness is not so noticeably reduced in the peripheral portion of the screen, so that the control for not executing the brightness correction is performed. Thus, when the entire screen is dark and it is not necessary to perform the luminance correction, the luminance correction is not performed, so that the power consumption can be reduced.
[0040]
【The invention's effect】
As described above, according to the cathode ray tube device of the present invention, the brightness correction control unit that controls the execution of the brightness correction is provided, and when the average screen brightness is less than the reference value, the output of the correction voltage output unit is turned off to set the brightness to OFF. Control not to execute correction. Therefore, for example, when the necessity of performing the luminance correction is low, such as in a screen where the entire screen is dark and the luminance decrease in the peripheral part of the screen is not so conspicuous, control not to execute the luminance correction is performed. Accordingly, power consumption can be effectively reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a cathode ray tube device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an overall configuration of a cathode ray tube device according to a second embodiment of the present invention.
FIG. 3 is a diagram showing an overall configuration of a cathode ray tube device according to a fourth embodiment of the present invention.
FIG. 4 is a diagram illustrating a luminance correction result of a cathode ray tube device according to a fourth embodiment.
[Explanation of symbols]
10 CRT device
20 CRT
30 RGB processor
40 Correction voltage output section
41 Correction voltage generation circuit
50 brightness correction control unit
51 Brightness detection circuit
52 comparator
53 OC

Claims (7)

In a cathode ray tube device that corrects a decrease in luminance at a peripheral portion of a screen by adding a correction voltage to a video signal,
Correction voltage output means for outputting the correction voltage in synchronization with scanning;
Brightness correction control means for controlling the execution of the brightness correction,
The brightness correction control means detects an average screen brightness in a predetermined time,
When the average screen luminance is less than the reference value, control is performed to turn off the output of the correction voltage output means. 2. The cathode ray tube apparatus according to claim 1, wherein said brightness correction control means includes a circuit for integrating an anode current, and detects an average screen brightness based on an integrated value of the anode current in a predetermined time. The brightness correction control means includes an automatic brightness limiting circuit that reduces the emission amount of the electron beam based on the integrated value of the anode current and limits the brightness, thereby preventing the high voltage circuit from being overloaded.
3. The cathode ray tube device according to claim 1, wherein the average screen luminance is detected based on an integrated value of the anode current detected by the automatic luminance limiting circuit. The correction voltage output means has a dynamic focus circuit that generates a focus voltage that gradually increases as the deflection angle of the electron beam increases,
4. The cathode ray tube device according to claim 1, wherein a dynamic focus voltage generated by the dynamic focus circuit is output as the correction voltage. The correction voltage output means,
The voltage applied to both ends of an S-shaped correction capacitor attached to an S-shaped correction circuit for correcting distortion of the deflection amount of an electron beam is output as the correction voltage. A cathode ray tube device according to claim 1. In a cathode ray tube device that corrects a decrease in luminance at a peripheral portion of a screen by adding a correction voltage to a video signal,
A cathode ray tube device, wherein a dynamic focus voltage generated by a dynamic focus circuit is used as the correction voltage. In a cathode ray tube device that corrects a decrease in luminance at a peripheral portion of a screen by adding a correction voltage to a video signal,
A cathode ray tube device, wherein a voltage applied to both ends of an S-shaped correction capacitor attached to an S-shaped correction circuit for correcting distortion of an electron beam deflection amount is used as the correction voltage.

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